Process for the preparation of piperidine

ABSTRACT

A PROCESS FOR THE PREPARATION OF PIPERIDINE IS DESCRIBED IN WHICH 4-CYANOBUTYRALDEHYDE IS HYDROGENATED IN THE PRESENCE OF A SUITABLE CATALYST AND AMMONIA.

United States Patent 3,658,824 PROCESS FOR THE PREPARATION OF PIPERIDINE1 Jozef A. Thoma, Sittard, and Johannes J. M. Deumens, Geleen,Netherlands, assignors to Stamicarbon N.V., Heerlen, Netherlands NoDrawing. Filed Mar. 30, 1970, Ser. No. 23,981 Int. Cl. C07d 29/06 US.Cl. 260-29352 Claims ABSTRACT OF THE DISCLOSURE A process for thepreparation of piperidine is described in which 4-cyanobutyraldehyde ishydrogenated in the presence of a suitable catalyst and ammonia.

The present invention relates to a process for the preparation ofpiperidine.

Several methods are presently known for the preparation of piperidine,but of these known methods only the preparation of piperidine by thereduction of pyridine, is of any practical importance. Even this method,however, has the disadvantage that pyridine is a rather expensivestarting material.

It has now been found that piperidine can be prepared quite economicallyaccording to the process of the present invention, whereby4-cyanobutyraldehyde is hydrogenated in the presence of a hydrogenationcatalyst and ammonia. The 4-cyanobutyraldehyde starting material forthis process may be prepared in a suitable maner from relativelyinexpensive basic materials such as acetaldehyde and acrylonitrile by aprocess, for example, according to application U.S. Ser. No. 8,704 filedFeb. 4, 1970 by the present applicants.

When practicing the process of the present invention, it is possible toachieve a yield of over 85% piperidine calculated on the basis of4-cyanobutyraldehyde. Such a high yield is particularly surprising inlight of prior experience with the catalytic hydrogenation of4-cyano-2,2- dimethylbutyraldehyde to 3,3-dimethylpiperidine as disclosed in German Auslegeschrift 1,222,931. When this latterhydrogenation is carried out in the presence of am-- monia, a yield ofno more than 25% is attained. On the other hand, when the samehydrogenation is carried out in the absence of ammonia, a higher yieldcan be realized, but in no event greater than 80%.

The amount of ammonia required in practicing the present invention isnot critical, and may be varied over a wide range. A favorable influenceon the yield can be noticed at an ammonia to 4-cyanobutyraldehyde molarratio as low as about 2:1. For optimum results, however, it ispreferable to use an ammonia to 4-cyanobutyraldehyde molar ratio withina range from about 5:1 to 25:1.

In practicing the process according to the present invention, variousknown and typical hydrogenation catalysts may be employed, such asnickel or cobalt on a carrier or in the form of a Raney-catalyst andcatalysts containing a platinum-metal such as platinum and palladium.

The present process can be carried out with or without an inert solvent.Examples of suitable solvents include water, lower alkanols such asmethanol, ethanol and isopropanol, and lower alkyl ethers, or mixturesof any of the above.

The present process is preferably carried out at a temperature in therange of between about 50 C. up to about 200 C., but most preferably ata temperature of about 80 to 150 C. A pressure in the range from about-1 to 300 atmospheres may be used but a pressure of 25 to 125atmospheres is preferable.

The resulting reaction product obtained by the present process consistsprimarily of piperidine. There may also be some by-product formation of1,5-diaminopentane, but this is not objectionable in that1,5-diaminopentane can be recovered and easily converted to piperidine,for example by a process as disclosed in Chemische Berichte, volume 95,1962, page 1992.

The process of the present invention can be carried out eithercontinuously or as a batch process by any of a number of knownhydrogenation methods. When a batch process is used, it is preferablycarried out by adding the 4- cyanobutyraldehyde to the ammonia-catalystmixture whilethe latter is kept under hydrogen pressure. In this way,the'by-product formation of 1,5-diaminopentane is minimized.

The following examples show some of the various means by which theinvention can be carried into practice, but are merely illustrative andare in no way intended to limit the scope of the invention.

EXAMPLE 1 Methanol (250 ml.) and ammonia (425 g., 25 moles) wereintroduced into a 5 l. autoclave provided with a stirrer and a feedline, along with a Raney nickel catalyst (30 g.). The ammonia wasintroduced by connecting the autoclave with a bomb containing liquidammonia. Hydrogen was fed into the autoclave until a pressure of 55atmospheres was reached whereupon this mixture in the autoclave washeated to 125 C. A solution of 4-cyanobutyraldehyde (121.3 g., 1.25moles) in methanol (750 ml.) was then added to the autoclave withsimultaneous stirring over a period of 1.5 hours while maintaining themixture temperature at 125 C. An additional 50 ml. of methanol was fedto the autoclave in order to wash out the feed "line. The temperaturewas then raised to 130 C. and maintained, with continuous stirring, forone hour. The mixture was then cooled to room temperature. The autoclavewas opened and ammonia was released, the catalyst recovered byfiltration and the methanol was recovered from the filtrate bydistillation whereby the ammonia dissolved in the filtrate was released.Benzene (250 g.) was then added to the remaining reaction product inorder to facilitate the removal of Water by azeotropic distillation. Theremaining product was then further distilled to yield a small quantityof benzene, 92 g. of piperidine (1.00 mole) having a boiling point103-105 C., and 14 g. of 1,5-diaminopentane (0.14 mole) having a boilingpoint of l75-178 C. The yield calculated on the basis of of4-cyanobutyraldehyde was 86.5% for the piperidine, and 11% for the1,5diaminopentane.

EXAMPLE 2 Methanol (350 ml.) and ammonia (170 g., 10 moles) wereintroduced into a 5 l. autoclave provided with a stirrer and fed line,along with a Raney nickel catalyst (40 g.). Hydrogen was fed into theautoclave until a pressure of 80 atmospheres Wes reached whereupon themixture in the autoclave was heated to 120 C. A solution of 4-cyanobutyraldehyde (121.3 g., 1.25 moles) in methanol (750 ml.) was thenadded to the autoclave with simultaneous stirring over a period of 2hours while maintaining the mixture temperature at 120 C. An additionalml. of methanol was fed to the autoclave in order to wash out the feedline. Stirring was then continued for another 1.5 hours whilemaintaining the mixture temperature at C. The mixture was then cooled toroom temperature. The autoclave was opened, the catalyst recovered byfiltration, and the filtrate Was dried with potassium hydroxide. Thedried solution was subsequently distilled resulting in the recovery ofmethanol, and a yield of 79.7 g. of piperidine (0.937 mole) having aboiling point of 104-105 (3., and 10.2 g. of 1,5-diaminopentane (0.1

3 mole) having a boiling point of 175-177 C. The yield calculated on thebasis of 4-cyanobuyraldehyde was 75% for the piperidine and 8% for the1,5-diaminopentane.

EXAMPLE 3 Methanol (400 ml.) and ammonia (380 g., 22.5 moles) wereintroduced into a l. autoclave provided with a stirrer and feed line,along with a Raney nickel catalyst (30 g.). Hydrogen was fed into theautoclave until a pressure of 115 atmospheres was reached whereupon thismixture in the autoclave was heated to 95 C. A solution of4-cyanobutyraidehyde (120 g. of impure 4-cyanobutyraldehyde, equivalentto 1.16 moles of pure 4-cyan'obutyraldehyde) in methanol (700 ml.) wasthen added to the autoclave with simultaneous stirring over a period of2 hours while maintaining the mixture at temperature of 95 C. Anadditional 50 ml. of methanol was fed to the autoclave in order to washout the feed line. The temperature in the autoclave was maintained at 95C. for an additional period of 2 hours with continuous stirring. Themixture was then cooled to room temperature. The autoclave was opened,the catalyst recovered by filtration, and the filtrate was dried withsodium sulphate. Distillation of the dried filtrate yielded 82.7 g. ofpiperidine (0.973 mole having) having a boiling point of 104-105 C., and12 g. of 1,5-diaminopentane (0.117 mole) having a boiling point of174-177 C. The yield calculated on the basis of 4-cyanobutyraldehyde was84% for the piperidine and for the 1,5-diaminopentane.

EXAMPLE 4 4-cyanobutyraldehyde (121.3 g., 1.25 moles) dissolved inmethanol (750 ml.), and ammonia (425 g., 25 moles) were fed into a 5 l.autoclave provided with a stirrer and feed line, along with a Raneynickel catalyst (40 g.). Hydrogen was fed into the autoclave until apressure of 60 atmospheres was reached. The mixture in the autoclave wasthen heated to 105 C. with simultaneous stirring over a period of 1 hourand thereafter maintained at this temperature for an additional hourwith continuous stirring. The mixture was then cooled to roomtemperature. The autoclave was opened, the catalyst recovered byfiltration, and the filtrate was dried with sodium sulphate. The driedfiltrate was then distilled to recover the methanol, and the remainingproduct contained 73.3 g. of piperidine (0.86 mole) having a boilingpoint of 103-1104 C. and 30.6 g. of 1,5-diaminopentane (0.3 mole) havinga boiling point of 174-177" C. The yield calculated on the basis ofA-cyanobutyraldehyde was 69% for the piperidine, and 24%. for the1,5-diaminopentane.

What is claimed is:

1. A process for the preparation of piperidine consisting essentially inthe hydrogenation of 4-cyanobutyraldehyde in the presence of ahydrogenation catalyst and ammonia wherein said hydrogenation is carriedout at a temperature of between and 200 C. and at a pressure of between1 and 300 atmospheres.

2. A process according to claim 1 wherein the hydrogenation is carriedout in the presence of a solvent.

3. A process according to claim 1 wherein the molar ratio of ammonia to4-cyanobutyraldehyde is at least 2:1.

4. A process according to claim 3 wherein the molar ratio of ammonia to4-cyanobutyraldehyde is at least 521 and no greater than 25:1.

5. A process according to claim 1 wherein said hydrogenation is carriedout in a batch reactor under a positive hydrogen pressure and said4-cyanobutyraldehyde is added to said ammonia and hydrogenation catalystwhile said ammonia and hydrogenation catalyst are under said positivehydrogen pressure.

References Cited UNITED STATES PATENTS 2,794,806 6/1957 Elam et al.260-293.2

FOREIGN PATENTS 1,222,931 '8/ 1966 Germany 260-293.2

HENRY R. JILES, Primary Examiner G. T. TODD, Assistant Examiner US. Cl.X.R. 2605 Patent NO. 3, 58, 2 Dated -A1 r11 25, 1972 lnventofls) JozefA. Thoma and Johannes J. M. Deumens It is certified that error appearsin the above-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, between lines 7 and 8, there should appear claims riority,application Netherlands, March 29, 1969, No- 69O I9O --3 line 32,"maner" should appear manner line 35 should read present assignee andone of the present co-applicants column 3, line 2;, l-cyanobuyraldehyde"should appear cyanobutymslldehyde line 25 "having", first occurrence,should be cancelled. v

Signed and sealed this l2 th da3 of December 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. 7 ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents ORM PC4050 (1069) USCOMM-DC scan-Poo U.$. GOVERNMENT PRINTINGOFFICE: 19 0"365'334,

